Rotary seal for an industrial fan assembly

ABSTRACT

A rotary seal for a rotating shaft passing through a stationary structure is mounted on the stationary structure and has at least two seal ring fabricated from resilient material and a cavity ring disposed within a seal housing bore of a seal housing. The cavity ring is disposed between the seal rings, and a seal cover compression ring compresses the seal rings and cause the seal rings to engage the seal housing bore to create a seal ring outer seal there between and to engage the rotating shaft to create a seal ring inner seal there between while allowing the rotating shaft to rotate relative to the seal ring. The seal housing has a pressurized inlet passage and the cavity ring includes cavity ring inlet passages allowing pressurized air or fluid to be supplied to the seal housing bore to prevent gases from leaking through the rotary seal.

TECHNICAL FIELD

The present disclosure relates generally to industrial fan assembliesand, more particularly, to a rotary seal for an fan shaft of anindustrial fan assembly.

BACKGROUND

Industrial fan assemblies are used in industrial applications to createfluid flow for processes such as combustion, ventilation, aeration,particulate transport, exhaust, cooling, air-cleaning, drying and airrecirculation. Fluid flow is created by rotating an impeller having aplurality of blades to create a reduced pressure at an inlet of the fanassembly to draw air in and an increased pressure at an outlet of thefan assembly to discharge air back into the operating environment.Typically, an industrial fan assembly includes a mounting structure onwhich a motor and a fan shaft are mounted. A transmission connects themotor to the shaft to convert rotation of a motor shaft of the motorinto corresponding rotation of the fan shaft. The impeller is mounted onor otherwise operatively connected to the fan shaft so that rotation ofthe fan shaft causes rotation of the impeller to generate the fluidflow.

Industrial fans may be generally categorized as being either centrifugalfans or axial fans depending on the flow path of the air passing therethrough. Centrifugal fans use the rotating impeller to draw air in,typically entering the impeller along an axial path parallel to arotational axis of the impeller. The air is then redirected to radialflow paths through the impeller blades and out of the fan assembly. Theairflow gains kinetic energy as the air moves radially outward towardthe impeller blade tips, and the kinetic energy is converted to a staticpressure increase beyond the impeller blades causing discharge the airthrough the fan outlet. Axial fans in contrast move fluid along therotational axis of the impeller. The fluid is pressurized by the axialforces, or aerodynamic lift, generated by the impeller blades.

The impeller blades of the industrial fan assemblies are subjected toloads and stresses during the operation of the fan assemblies. Where theindustrial fan assemblies are implemented in high temperatureenvironments, the impeller blades are further subjected to thermalstresses that, along with the other loads and stresses, can cause theimpeller blades to change shape from having a formed radius and bladetwist for optimum performance, and thereby result in reduced efficiencyand unwanted vibration. These changes can also result in increased soundlevels, increased turbulence past the impeller that increases theresistance of the system and the static pressure against which the fanoperates. The components of the industrial fan assemblies may also beaffected by chemicals and by-products in corrosive atmospheres.Ultimately, the additional thermal stresses and other adverse conditionscan result in earlier fatigue failure of the impeller and more frequentneed for replacement in high temperature environments as the fan enduresnumerous thermal cycles from process and in corrosive environments dueto exposure to harmful chemicals than when operating in environmentsthat do not cause the same level of thermal stresses or corrosiveexposure on the impellers.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, a rotary seal for a rotatingshaft passing through a stationary structure is disclosed. The rotaryseal includes a seal housing having a seal housing outer surface, a sealhousing inner surface defining a seal housing bore having a seal housinglongitudinal axis, a seal housing mounting end secured to the stationarystructure about a shaft opening through which the rotating shaft isinserted, and a seal housing sealing end opposite the seal housingmounting end, a seal ring fabricated from a resilient material anddisposed within the seal housing bore and engaged by the seal housinginner surface to prevent the seal ring from passing out of the sealhousing bore through the seal housing mounting end, a seal cover havinga seal cover flange and a seal cover compression ring extending downwardfrom the seal cover flange and having a compression ring outer diameterthat is less than a seal housing bore inner diameter proximate the sealhousing sealing end so that the seal cover compression ring is insertedinto the seal housing bore and engages the seal ring, and a seal coveranchor mechanism engaging the seal cover and the seal housing to securethe seal cover to the seal housing. The seal cover anchor mechanismcauses the seal cover compression ring to compress the seal ring andcause the seal ring to engage the seal housing inner surface to create aseal ring outer seal there between and to engage the rotating shaft tocreate a seal ring inner seal there between while allowing the rotatingshaft to rotate relative to the seal ring.

In another aspect of the present disclosure, a rotary seal for arotating shaft passing through a stationary structure is disclosed. Therotary seal includes a seal housing having a seal housing outer surface,a seal housing inner surface defining a seal housing bore having a sealhousing longitudinal axis, a seal housing mounting end secured to thestationary structure about a shaft opening through which the rotatingshaft is inserted, and a seal housing sealing end opposite the sealhousing mounting end, a first seal ring fabricated from a resilientmaterial and disposed within the seal housing bore proximate the sealhousing sealing end, and a second seal ring fabricated from theresilient material and disposed within the seal housing bore proximatethe seal housing mounting end and engaged by the seal housing innersurface to prevent the second seal ring from passing out of the sealhousing bore through the seal housing mounting end. The rotary sealfurther includes a cavity ring disposed within the seal housing borebetween the first seal ring and the second seal ring, wherein the cavityring has a cavity ring outer diameter that is less than a seal housingbore inner diameter and a cavity ring inner diameter that is greaterthan a shaft outer diameter, a seal cover having a seal cover flange anda seal cover compression ring extending downward from the seal coverflange and having a compression ring outer diameter that is less thanthe seal housing bore inner diameter proximate the seal housing sealingend so that the seal cover compression ring is inserted into the sealhousing bore and engages the first seal ring, and a seal cover anchormechanism engaging the seal cover and the seal housing to secure theseal cover to the seal housing. The seal cover anchor mechanism causesthe seal cover compression ring to compress the first seal ring and thesecond seal ring and cause the first seal ring and the second seal ringto engage the seal housing inner surface to create seal ring outer sealsthere between and to engage the rotating shaft to create seal ring innerseals there between while allowing the rotating shaft to rotate relativeto the first seal ring and the second seal ring.

In a further aspect of the present disclosure, a rotary seal for arotating shaft passing through a stationary structure is disclosed. Therotary seal includes a seal housing having a seal housing outer surface,a seal housing inner surface defining a seal housing bore having a sealhousing longitudinal axis, a seal housing mounting end secured to thestationary structure about a shaft opening through which the rotatingshaft is inserted, and a seal housing sealing end opposite the sealhousing mounting end, a cavity ring disposed within the seal housingbore, a first seal ring fabricated from a resilient material anddisposed within the seal housing bore between the cavity ring and theseal housing sealing end, a second seal ring fabricated from theresilient material, disposed within the seal housing bore proximatebetween the cavity ring and the seal housing mounting end and engaged bythe seal housing inner surface to prevent the second seal ring frompassing out of the seal housing bore through the seal housing mountingend, and a third seal ring fabricated from the resilient material anddisposed within the seal housing bore between the cavity ring and thesecond seal ring. The cavity ring has a cavity ring outer diameter thatis less than a seal housing bore inner diameter and a cavity ring innerdiameter that is greater than a shaft outer diameter, and a plurality ofcavity ring inlet passages extending through the cavity ring from acavity ring outer surface to a cavity ring inner surface. The sealhousing comprises a pressurized inlet passage extending through the sealhousing from the seal housing outer surface to the seal housing innersurface, and wherein the cavity ring is aligned with the pressurizedinlet passage so that the pressurized inlet passage and the cavity ringinlet passages place the cavity ring inner surface and a correspondingportion of the rotating shaft in fluid communication with a pressurizedfluid source fluidly connected to the pressurized inlet passage. Therotary seal further includes a seal cover having a seal cover flange anda seal cover compression ring extending downward from the seal coverflange and having a compression ring outer diameter that is less thanthe seal housing bore inner diameter proximate the seal housing sealingend so that the seal cover compression ring is inserted into the sealhousing bore and engages the first seal ring, and a seal cover anchormechanism engaging the seal cover and the seal housing to secure theseal cover to the seal housing. The seal cover anchor mechanism causesthe seal cover compression ring to compress the first seal ring, thesecond seal ring, and the third seal ring, and cause the first sealring, the second seal ring and the third seal ring to engage the sealhousing inner surface to create seal ring outer seals there between andto engage the rotating shaft to create seal ring inner seals therebetween while allowing the rotating shaft to rotate relative to thefirst seal ring, the second seal ring and the third seal ring.

Additional aspects are defined by the claims of this patent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an industrial fan assembly including anembodiment of a fan mount assembly in accordance with the presentdisclosure;

FIG. 2 is an isometric view of an industrial fan assembly including analternative embodiment of a fan mount assembly in accordance with thepresent disclosure;

FIG. 3 is an exploded isometric view of the industrial fan assembly ofFIG. 1;

FIG. 4 is an isometric view of an embodiment of an impeller of theindustrial fan assembly of FIG. 1 in accordance with the presentdisclosure;

FIG. 5 is a top view of the impeller of FIG. 4;

FIG. 6 is a top view of the impeller of FIG. 4 with a top impeller ringremoved to reveal a top impeller blade deck;

FIG. 7 is an isometric exploded view of the impeller of FIG. 4;

FIG. 8 is an isometric view of an alternative embodiment of an impellerof the industrial fan assembly of FIG. 1 in accordance with the presentdisclosure;

FIG. 9 is a top view of the impeller of FIG. 8 with an impeller ringremoved to reveal an impeller blade deck;

FIG. 10 is an isometric exploded view of the impeller of FIG. 8;

FIG. 11 is an isometric exploded view of a shaft end and an impeller hubof the industrial fan assembly of FIG. 1;

FIG. 12 is an isometric view of a further alternative embodiment of animpeller of the industrial fan assembly of FIG. 1 in accordance with thepresent disclosure;

FIG. 13 is an end view of the impeller of FIG. 12;

FIG. 14 is an end view of the impeller of FIG. 12 with a hub sprocketremoved;

FIG. 15 is an isometric exploded view of the impeller of FIG. 12;

FIG. 16 is an isometric view of a further alternative embodiment of animpeller of the industrial fan assembly of FIG. 1 in accordance with thepresent disclosure;

FIG. 17 is an end view of the impeller of FIG. 16;

FIG. 18 is an opposite end view of the impeller of FIG. 16;

FIG. 19 is a side view of the impeller of FIG. 16;

FIG. 20 is a cross-sectional view of the impeller of FIG. 16 takenthrough line 20-20 of FIG. 17;

FIG. 21 is an isometric exploded view of the impeller of FIG. 16;

FIG. 22 is an isometric exploded view of a rotary seal in accordancewith the present disclosure for the industrial fan assemblies of FIGS. 1and 2;

FIG. 23 is a cross-sectional view of the rotary seal of FIG. 22 takenthrough line 23-23 of FIG. 22;

FIG. 24 is the cross-sectional view of the rotary seal of FIG. 23 with afan shaft inserted through the rotary seal and with a seal coverdetached from a seal housing of the rotary seal; and

FIG. 25 is the cross-sectional view of the rotary seal of FIG. 23 withthe fan shaft inserted through the rotary seal and with the seal coverattached to the seal housing and compressing seal rings disposed withinthe seal housing.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary configuration of an industrial fanassembly 10 that may be implemented in high temperature applications.The industrial fan assembly 10 may include a fan mount assembly 12supporting a motor 14, a fan shaft 16 (FIG. 3), and a transmission 18connecting the motor 14 to the fan shaft 16. The fan assembly 10 furtherincludes an impeller 20, such as the forward curve wheel hub impeller 20shown in FIG. 1, mounted to an end of the fan shaft 16 opposite thetransmission 18. The impeller 20 may be installed within a hightemperature area such as a furnace or curing station, while the othercomponents of the industrial fan assembly 10 are disposed external tothe high temperature environment. An insulation dam assembly 22 may bepositioned on the fan shaft 16 between the fan mount assembly 12 and theimpeller 20, and mounted to a wall or other interface between the hightemperature and low temperature areas to reduce or prevent heat transferacross the interface. The insulation dam assembly 22 can also preventinfiltration of the ambient atmosphere into the environment of theimpeller 20 from negative pressure created by the spinning of theimpeller 20, and vice versa where the impeller 20 is disposed within apressurized environment.

FIG. 2 illustrates an alternative free-standing configuration of anindustrial fan assembly 30 typically used in exhausting applications andhaving a fan mount assembly 32, a motor 34, a fan shaft 36 and atransmission 38 configured to specific applications. FIG. 2 more clearlyillustrates the motor shaft 40 of the motor 34 and the fan shaft 36connected by the transmission 38, and the fan shaft 36 being rotatablymounted on the fan mount assembly 32 by shaft bearings 42. An impeller(not shown) such as the impeller 20 or other appropriate impeller suchas those illustrated and described further hereinafter, may be mountedto the fan shaft 36 opposite the transmission 38 and disposed within afan housing 44. The fan housing 44 may be insulated and function similarto the insulation dam assembly 22 with regard to limiting heat transferbetween the high temperature and low temperature areas to ensureworkforce safety and protect personnel from burn hazards even inimplementations where the high temperature environment can havetemperatures in excess of 1,800° F. The fan housing 44 includes a fanhousing inlet 46 for drawing air to the impeller, and a fan housingoutlet 48 for expelling air from the fan housing 44. The fan housing 44may include additional fan housing outlets 48 circumferentially spacedabout the fan housing 44 to offer alternate discharge directionsdepending on the requirements of a particular customer installation. Inthis arrangement, the centrifugal flow impeller and the fan housing 44change the direction of airflow by 90° from the fan housing inlet 46 tothe fan housing outlet 48. When axial flow impellers are used, such asthose described below, the fan housing 44 or other airflow controlstructures may be used to cause inlet air and outlet air to flow in theaxial direction through the axial flow impeller relative to the fanshaft 16, 36 and the rotation of the impeller. The fan housing 44 mayfurther include lift brackets 50 to which cables, chains, pulleys,cranes or other positioning mechanisms may be attached to transport andposition the fan housing 44 during installation.

Additional details of the fan assembly 10 of FIG. 1 are shown in theexploded view of FIG. 3. The fan mount assembly 12 is shown with thecomponents detached and separated, including components welded togetherin the final assembly of the fan mount assembly 12. The fan mountassembly 12 includes a top plate 60, a first side plate 62 and a secondside plate 64 as main structural components. The top plate 60 has a topplate top surface 66, a top plate bottom surface 68, and a first topplate lateral edge 70 and a second top plate lateral edge 72 disposed onopposite sides of the top plate 60. One or more top plate slots 74extend through the top plate 60 proximate the first top plate lateraledge 70, and one or more top plate slots 76 extend through the top plate60 proximate the second top plate lateral edge 72.

The first side plate 62 and the second side plate 64 may be generallyplanar, but may include some contouring to accommodate other structuralelements and components attached to the fan mount assembly 12. The firstside plate 62 has a first side plate inner surface 80, a first sideplate outer surface 82 and a first side plate top edge 84. The firstside plate 62 further includes one or more first side plate tabs 86extending upward from the first side plate top edge 84. Each of thefirst side plate tabs 86 corresponds in size and position with one ofthe top plate slots 74. The second side plate 64 may be a mirror imageof the first side plate 62, and includes a second side plate innersurface 90, a second side plate outer surface 92, a second side platetop edge 94 and one or more second side plate tabs 96 extending upwardfrom the second side plate top edge 94 and each corresponding in sizeand position with one of the top plate slots 76. The main portion of thefan mount assembly 12 may be assembled by inserting the side plate tabs86, 96 upward through the corresponding top plate slots 74, 76,respectively, until the side plate top edges 84, 94 engage the top platebottom surface 68. The top plate slots 74, 76 and the side plate tabs86, 96 may be dimensioned for a relatively close fit so that the sideplates 62, 64 are at approximately their proper alignment relative tothe top plate 60 when the side plate top edges 84, 94 engage the topplate bottom surface 68.

Further precise alignment of the side plates 62, 64 relative to the topplate 60 may be achieved with additional support structures. Forexample, tab gussets 100 may be welded to the top plate top surface 66and corresponding portions of the side plate inner surfaces 80, 90 foreach of the side plate tabs 86, 96, respectively, after the side platetabs 86, 96 are inserted through the top plate slots 74, 76. Upperstructural support brackets 102 may be connected between the side plateinner surfaces 80, 90 of the side plate tabs 86, 96 positioned acrossfrom each other after the side plate tabs 86, 96 are inserted throughthe top plate slots 74, 76. One or more lower structural supportbrackets 104 may be connected between the side plate inner surfaces 80,90 below the top plate bottom surface 68 before or after the side platetabs 86, 96 are inserted through the top plate slot 74, 76. Thestructural support brackets 102, 104 may have lengths that areapproximately equal to a distance between the top plate slots 74, 76 sothat the side plates 62, 64 are approximately parallel when the fanmount assembly 12 is assembled.

In the illustrated embodiment, the fan shaft 16 is mounted to the topplate bottom surface 68 by a pair of shaft bearings 110 that may besecured by shaft bearing mounting bolts 112 or other appropriatefastening means. The fan shaft 16 extends beyond the top plate 60 andthe side plates 62, 64 at both ends. A first shaft end 114 of the fanshaft 16 extends through a heat slinger 116 that is mounted on the fanshaft 16 to act as a heat sink and dissipate heat from the hightemperature area. The first shaft end 114 further extends through theinsulation dam assembly 22 and has the impeller 20 mounted thereon sothat the insulation dam assembly 22 is disposed between the fan mountassembly 12 and the impeller 20.

A second shaft end 118 of the fan shaft 16 is received into thetransmission 18 through a transmission fan shaft opening 120. A motorshaft 122 of the motor 14 is received into the transmission 18 by atransmission motor shaft opening 124. The second shaft end 118 and themotor shaft 122 are operatively connected to the internal components ofthe transmission 18 so that rotation of the motor shaft 122 causes acorresponding rotation of the fan shaft 16 and the impeller 20. Thetransmission 18 may include belts, chains or other torque transfercomponents that must be loaded to create sufficient attention to preventslippage in the transmission 18. Consequently, the transmission motorshaft opening 124 may be an elongated slot that allows the distancebetween the second shaft end 118 and the motor shaft 122 to be varied asnecessary to create the required tension in the components of thetransmission 18.

Adjustment of the position of the motor shaft 122 is accomplished in thefan mount assembly 12 by providing a movable motor mounting bracket 130to which the motor 14 is mounted with motor mounting bolts 132 and motormounting nuts 134 or other appropriate fastening means. The motormounting bracket 130 as illustrated includes a motor mounting plate 136with a motor plate top surface 138 to which the motor 14 is secured, amotor plate bottom surface 140, a first motor plate lateral edge 142 anda second motor plate lateral edge 144 opposite the first motor platelateral edge 142. A first motor height adjustment plate 146 extendsdownward from the first motor plate lateral edge 142 and has verticalmotor height adjustment slots 148 there through, and a second motorheight adjustment plate 150 extends downward from the second motor platelateral edge 144 and also has vertical motor height adjustment slots 152extending there through. The first side plate tabs 86 include motorheight adjustment apertures 154 that can be aligned with the motorheight adjustment slots 148 and the second side plate tabs 96 includemotor height adjustment apertures 156 that can be aligned with the motorheight adjustment slots 152. When the motor height adjustment apertures154, 156 are aligned with the motor height adjustment slots 148, 152,respectively, motor height adjustment bolts 158 may be inserted throughthe pairs of motor height adjustment apertures 154, 156 and motor heightadjustment slots 148, 152 and secured therein by the motor heightadjustment nuts 160. The height of the motor 14 and the motor mountingplate 136 above the top plate 60, and correspondingly the distancebetween the second shaft end 118 and the motor shaft 122, is set bypositioning the motor mounting bracket 130 relative to the top plate 60and securing the first motor height adjustment plate 146 to the firstside plate tabs 86 and the second motor height adjustment plate 150 tothe second side plate tabs 96 with the motor height adjustment bolts 158and the motor height adjustment nuts 160. If additional structuralsupport as necessary, motor mounting plate gussets 162 may be installedon the motor plate bottom surface 140 and the motor height adjustmentplates 146, 150 at locations that will not cause interference with themovement of the motor height adjustment plates 146, 150 relative to theside plate tabs 86, 96.

The fan mount assembly 12 may be secured to the insulation dam assembly22 to form a single unitary component. In one embodiment, a top plateend edge 164, a first side plate end edge 166 and a second side plateend edge 168 may be secured to an outer surface of an insulation dammounting plate 170, such as by welding. Further structural support maybe provided by wing gussets 172 secured between the top plate topsurface 66 and the insulation dam mounting plate 170. One of the winggussets 172 may be proximate the first top plate lateral edge 70 and bealigned approximately above the first side plate top edge 84, and theother wing gusset 172 may be proximate the second top plate lateral edge72 and be aligned approximately above the second side plate top edge 94.In alternative embodiments, the wing gussets 172 may be additional sideplate tabs 86, 96 extending upward from the side plate top edges 84, 94,respectively. The top plate 60 may have additional top plate slots 74,76 at the top plate end edge 164 that align with the wing gussets172/side plate tabs 86, 96. The wing gussets 172 may be inserted throughthe top plate slots 74, 76 along with the other side plate tabs 86, 96and then secured to the insulation dam mounting plate 170 by welding orother securement means.

The fan mount assembly 12 may facilitate installation by providingmultiple points of attachment for lifting or transportation equipment.Consequently, the top plate 60 may have top plate lift openings 174proximate the transmission 18, and the side plates 62, 64 may have sideplate lift openings 176 proximate both the transmission 18 and theinsulation dam assembly 22. The motor mounting bracket 130 may havemotor mounting bracket lift openings 178 on each of the motor heightadjustment plates 146, 150, and the wing gussets 172 may have a winggusset lift openings 180. Each of the lift openings 174-180 may be sizedfor attachment of a rope, chain, hook or other lift or transportationmechanism connection. The fan mount assembly 12 may further facilitateaccess to the interior of the fan mount assembly 12 via access apertures182 through the side plates 62, 64. The access apertures 182 can provideconvenient access points for bearing lubrication stations for providinglubricant to the shaft bearings 110 without disassembling any componentsof the fan mount assembly 12 or removing shaft safety guards 184, 186that may be installed to cover the fan shaft 16. The access apertures182 may also provide a point of access for providing gas to or purginggas from a rotary seal (see FIGS. 22-25 and accompanying discussionbelow) that substantially prevents airflow between the high temperatureor corrosive environment and the ambient environment.

FIGS. 4-7 illustrate an embodiment of the impeller 20 of the industrialfan assembly 10. The impeller 20 is a forward curved wheel impeller thatis configured for extended use in high temperature environments. Theimpeller 20 may include one or more levels or decks of impeller bladesmounted on an impeller hub assembly. In the illustrated embodiment, theimpeller has three impeller blade decks. Referring to FIG. 4, theimpeller 20 includes an impeller hub assembly 200 having a hub shaftbore 202 for receiving the first shaft end 114 of the fan shaft 16. Thehub shaft bore 202 has a bore longitudinal axis 204 about which theimpeller hub assembly 200 and the other components of the impeller 20are symmetrical to facilitate rotation substantially free of vibration.

The impeller 20 further includes an impeller baseplate 210 mounted onthe impeller hub assembly 200. The impeller baseplate 210 has an annularshape, a baseplate bottom surface facing and secured to the impeller hubassembly 200, and a baseplate top surface opposite the baseplate bottomsurface. A first or bottom impeller blade deck 212 is formed by aplurality of first impeller blades 214 that are secured to and extendupward from the baseplate top surface. The first impeller blades 214 arecircumferentially spaced about the bore longitudinal axis 204 and theimpeller baseplate 210. A first impeller ring 216 is secured to thefirst impeller blades 214 opposite the impeller baseplate 210. Similarto the impeller baseplate 210, the first impeller ring 216 has anannular shape, a first ring bottom surface facing and engaging the firstimpeller blades 214, and a first ring top surface opposite the firstring bottom surface. A second impeller blade deck 218 is formed by aplurality of second impeller blades 220 extending between the first ringtop surface and a second ring bottom surface of a second impeller ring222, and a third impeller blade deck 224 is formed by a plurality ofthird impeller blades 226 extending between the second ring top surfaceand a third ring bottom surface of a third impeller ring 228. Threeimpeller blade decks 212, 218, 224 are shown in the illustratedembodiment, but the impeller 20 in accordance with the presentdisclosure may have more or fewer impeller blade decks depending on therequirements for the high temperature application.

As shown in the top views of FIG. 5 and FIG. 6 (third impeller ring 228removed), the impeller baseplate 210 and the impeller rings 216, 222,228 may have approximately equal outer diameters. The impeller rings216, 222, 228 may have approximately equal inner diameters, while theimpeller baseplate 210 may have a smaller inner diameter to providegreater surface area on the baseplate bottom surface for engagement withthe impeller hub assembly 200. In alternative embodiments, the outerdiameters and the inner diameters of the impeller baseplate 210 and theimpeller rings 216, 222, 228 may not be equal depending on therequirements of a particular implementation.

FIGS. 4 and 6 illustrate the distribution and alignment of the impellerblades 214, 220, 226 within and between the impeller blade decks 212,218, 224. As mentioned previously, the impeller blades 214, 220, 226 ofeach impeller blade deck 212, 218, 224 are circumferentially spacedabout the bore longitudinal axis 204 is best seen in FIG. 6 for thethird impeller blade deck 224. Moreover, each impeller blade 214, 220,226 is longitudinally aligned with corresponding impeller blades 214,220, 226 in the adjacent decks as is most apparent from FIG. 4. Each ofthe impeller blades 214, 220, 226 has a curved shape in across-sectional plane perpendicular to the bore longitudinal axis 204for efficient discharge of air from the industrial fan assembly 10. Atthe same time, the impeller blades 214, 220, 226 extend generallyradially outward relative to the bore longitudinal axis 204 fromcorresponding inner edges of the impeller rings 216, 222, 228. Thoseskilled in the art will understand that the impeller blades 214, 220,226 may have alternative geometric configurations, and may even be flator planar, and may have different orientations relative to the borelongitudinal axis 204.

During use, the impeller blades 214, 220, 226 are subjected to inertialloads and stress loads caused by the rotation of the components of theimpeller 20 and the forces required to redirect the airflow.Additionally, thermal stresses are created due to the high temperatureenvironment. With the thin profiles of the impeller blades 214, 220,226, over time, the combination of stresses can cause the impellerblades 214, 220, 226 to flatten out, leading to decreased efficiency,imbalance causing vibration, and ultimately failure of the impellerblades 214, 220, 226.

To reduce the stresses experienced by the impeller blades 214, 220, 226,the impeller 20 in accordance with the present disclosure includesadditional support structures. As seen in FIGS. 4 and 6, the impeller 20includes a plurality of reinforcement bars 230 extending from andsecured to the impeller baseplate 210 and to the third impeller ring216. The reinforcement bars 230 are circumferentially spaced about thebaseplate top surface and the third impeller ring bottom surface topreserve the balance of the impeller 20. There are fewer reinforcementbars 230 than impeller blades 214, 220, 226 in each impeller blade deck212, 218, 224, and each reinforcement bar 230 is aligned withcorresponding ones of the impeller blades 214, 220, 226 in each impellerblade deck 212, 218, 224.

The reinforcement bars 230 are engaged by and secured to thecorresponding impeller blades 214, 220, 226. As a result, each group ofimpeller blades 214, 220, 226 in each impeller blade deck 212, 218, 224has two types of impeller blades. Full impeller blades 232 (FIG. 6) arenot aligned with any of the reinforcement bars 230, while reinforcementblades 234 are aligned with the reinforcement bars 230. The fullimpeller blades 232 extend radially outward to a position proximate theouter edges of the impeller rings 216, 222, 228, while the reinforcementblades 234 accommodate the reinforcement bars 230 that are positionedradially outward of the reinforcement blades 234 in the illustratedembodiment. Consequently, the reinforcement blades 234 have a shorterlength than the full impeller blades 232 in the radial direction. Asillustrated, each impeller blade deck 212, 218, 224 includes forty-eighttotal impeller blades 214, 220, 226, with forty-four being full impellerblades 232 and four being reinforcement blades 234 corresponding to thefour reinforcement bars 230. Depending on the configuration of theimpeller 20 and the requirements of an implementation of the industrialfan assembly 10, the impeller 20 may have more or fewer impeller blades214, 220, 226 and reinforcement bars 230, and a ratio of the impellerblades 214, 220, 226 per impeller blade deck 212, 218, 224 to thereinforcement bars 230 of greater than or less than the 12-to-1 ratio inthe present embodiment.

FIG. 7 presents an exploded view of the impeller 20 to furtherillustrate the configuration of the impeller rings 216, 222 and thereinforcement bars 230. The first impeller ring 216 has a plurality offirst reinforcement bar apertures 236 and the second impeller ring 222has a plurality of second reinforcement bar apertures 238circumferentially spaced about the impeller rings 216, 222. Duringassembly, the reinforcement bar apertures 236, 238 are aligned and thereinforcement bars 230 are inserted there through and secured to theimpeller rings 216, 222, the baseplate top surface and the third ringbottom surface by welding or other securement means. In alternativeembodiments, the reinforcement bar apertures 236, 238 may be omitted andthe reinforcement bars 230 may be replaced by shorter reinforcement barshaving longitudinal links approximately equal to the longitudinal linksof the impeller blades 214, 220, 226 and secured between the top andbottom surfaces of the impeller baseplate 210 and the impeller rings216, 222, 228.

FIG. 7 also illustrates one embodiment of the impeller hub assembly 200.The impeller hub assembly 200 as shown includes an impeller hub 240having a cylindrical shape, a hub outer surface and the hub shaft bore202. The impeller hub assembly 200 further includes an impeller hubbackplate 242 having a hub backplate top surface and a hub backplatebottom surface opposite the hub backplate top surface. The impeller hub240 is mounted to and is concentric with the impeller hub backplate 242,and the hub backplate top surface is facing, secured to and concentricwith the baseplate bottom surface. An impeller hub cone is formed by afirst hub half cone 244 and a second hub half cone 246. When assembled,the impeller hub cone has a large diameter cone end 248 and asmall-diameter cone end 250. The large diameter cone end 248 is securedto the hub backplate top surface and is concentric with the impeller hub240 and the impeller hub backplate 242. The impeller hub 240 extendsthrough the smaller diameter cone end 250. The shape of the impeller hubcone promotes redirection of the airflow from an axial airflow when theair is entering the fan housing inlet 46 and the impeller 20 to radialairflow to the impeller blades 214, 220, 226 and out of the fan housingoutlet 48. The impeller hub assembly 200 may further include a pluralityof hub gussets 252 that are circumferentially spaced about the impellerhub 240 and disposed between the hub backplate top surface and theimpeller hub cone. The hub gussets 252 extend between and are secured tothe hub outer surface and the hub backplate top surface. In alternativeembodiments, the impeller hub cone could be a single unitary component,and the impeller baseplate 210 may be omitted and the reinforcement bars230 and the impeller blades 214 of the first impeller blade deck 212 maybe secured directly to the hub backplate top surface.

FIGS. 8-10 illustrate an alternative embodiment of an impeller 260 inthe form of a backward inclined impeller having a single impeller bladedeck 262 of a plurality of impeller blades 264. In this embodiment,components corresponding to components of the impeller 20 are identifiedwith the same reference numerals, such as the impeller hub assembly 200,the impeller baseplate 210 and the reinforcement bars 230. In thisembodiment, the impeller blades 264 are configured as thin platesoriented at an angle relative to radial lines extending outwardly fromthe bore longitudinal axis 204 and passing through the impeller blades264 as shown in the top view of FIG. 9.

The number of reinforcement bars 230 is less than the number of impellerblades 264, so the impeller blade deck 262 includes full impeller blades266 that are not aligned with the reinforcement bars 230, andreinforcement blades 268 aligned with the reinforcement bars 230 andbeing shorter than the full impeller blades 266. The reinforcement bars230 extend to a bottom surface of an impeller ring 270 (FIG. 8) that hasa conical shape that is apparent in FIGS. 8 and 10. To accommodate theconical shape of the impeller ring 270, the impeller blades 264 have anaxial length that varies from a maximum at a radially inward most end toa minimum at a radially outward most end.

Due to their planar configuration and relatively large axial length, theimpeller blades 264 may be more susceptible to deformation whensubjected to torsional and thermal stresses during operation. Theimpeller blades 264 may be further reinforced by providing a bladesupport ring 272 between the impeller baseplate 210 and the impellerring 270. The blade support ring 272 may have a blade slot 274corresponding to each of the impeller blades 264, with the blade slots274 being circumferentially spaced about the blade support ring 272. Theblade support ring 272 may be positioned approximately halfway betweenthe impeller baseplate 210 and the impeller ring 270 and welded orotherwise secured to the impeller blades 264 and the reinforcement bars230. For each of the reinforcement blades 268, the corresponding bladeslots 274 may be configured to have the reinforcement bar 230 passthrough the blade support ring 272.

FIG. 11 illustrates an impeller attachment arrangement for securing theimpellers 20, 260, and other impellers discussed herein can be reliablymounted to the first shaft end 114 of the fan shaft 16. The fan shaft 16has a greater outer diameter than an inner diameter of the hub shaftbore 202. To be received into the hub shaft bore 202, the first shaftend 114 may have an impeller landing 280 machined down to an outerdiameter that is less than the inner diameter of the hub shaft bore 202.The impeller landing 280 may have an axial length that is approximatelyequal to, or approximately ⅛″ to ¼″ less than, an axial length of theimpeller hub 240, and terminate at an impeller landing shoulder 282.When one end of the impeller hub 240 slides onto the impeller landing 28to the impeller landing shoulder 282, the first shaft end 114 will beapproximately flush with or slightly recessed from the opposite end ofthe impeller hub 240. The key 284 will be disposed within a keyway 286of the impeller hub 240 and a key seat 288 of the impeller landing 280to lock the impeller hub 280 and the fan shaft 16 for rotation together.

Set screws (not shown) tightened down in set screw apertures 290 willsubstantially prevent the impeller hub 240 from sliding axially awayfrom the impeller landing shoulder 282. Further positive retention inthe axial direction may be provided by an impeller retention plate 292.The impeller retention plate 292 may have an outer diameter greater thanthe inner diameter of the hub shaft bore 202 so that an outer edge ofthe impeller retention plate 292 extends beyond the hub shaft bore 202and engages the end of the impeller hub 240. A retention bolt opening294 is drilled in the first shaft end 114 and receives an impellerretention bolt 296. After the first shaft end 114 is inserted throughthe hub shaft bore 202, the impeller retention plate 292 is bolted tothe first shaft end 114 to capture the impeller hub 240 between theimpeller landing shoulder 282 and the impeller retention plate 292.

FIGS. 12-15 illustrate an alternative embodiment of a centrifugalimpeller 300 in accordance with the present disclosure that may beimplemented in the industrial fan assemblies 10, 30 in the form of aradial blade impeller 300. The impeller 300 includes an impeller hub 302that may have a similar configuration as the impeller hub 240illustrated and described above with a cylindrical shape, a hub outersurface 304 and a hub shaft bore 306 with a hub longitudinal axis 308about which the impeller 300 rotates. The impeller 300 further includesa plurality of impeller blade assemblies 310 (e.g., six in theillustrated embodiment) circumferentially spaced about, secured to andextending outward from the hub outer surface 304. Each of the impellerblade assemblies 310 has a leading blade assembly surface 312 facing adirection of rotation 314 (FIG. 13) of the impeller 300 and a trailingblade assembly surface 316 opposite the leading blade assembly surface312.

Each impeller blade assembly 310 may be a single unitary component insome embodiments. In the illustrated embodiment, however, the impellerblade assemblies 310 are formed from multiple component elements. Eachimpeller blade assembly 310 includes a blade arm 320 and an impellerblade 322 connected thereto. Each blade arm 320 has an inward arm edgesecured to the hub outer surface 304 and extends approximately radiallyoutward to an outward arm edge. Each blade arm 320 has a leading armsurface facing the direction of rotation 314 and a trailing arm surfaceopposite the leading arm surface, and has oppositely disposed lateralarm edges having an arm width there between that is less than alongitudinal length of the impeller hub 302.

Each impeller blade 322 has a leading blade surface facing the directionof rotation 314 and a trailing blade surface opposite the leading bladesurface and facing and engaging the leading arm surface of thecorresponding blade arm 320. The impeller blades 322 are oriented withan inward blade edge proximate the hub outer surface 304, and with theimpeller blades 322 extending approximately radially outward to anoutward blade edge. The impeller blades 322 have oppositely disposedlateral blade edges having a blade width that is greater than or equalto the arm width.

The impeller blades 322 may be configured to efficiently draw air inthrough the fan housing inlet 46 and discharge air from the fan housingoutlet 48. Each impeller blade 322 may include a blade tapered portion324 (FIG. 15) proximate the blade inward edge and a blade rectangularportion 326 proximate the blade outward edge. In the blade taperedportion 324, the blade width between the blade lateral edges mayincrease as the blade tapered portion 324 extends away from the bladeinward edge and the hub outer surface 304. In the blade rectangularportion 326, the blade width may be constant as the blade rectangularportion 326 extends radially outward from the blade tapered portion 324to the blade outward edge. Within the blade rectangular portion 326, animpeller blade bend 328 parallel to the hub longitudinal axis 308 mayrotate the blade outward edge forward toward the direction of rotation314 by an angle θ (FIG. 14). Depending on the implementation, the angleθ may be within the range from 10° to 40°, and may typically beapproximately 30°. Forming the impeller blade bend 328 with the angle θin the direction of rotation 314 may increase the overall strength ofthe impeller blades 322, and help prevent deformation or effects of theimpeller blades 322 losing their straight edges due to torsionalstresses or deformation cause by continuous operation in hightemperature, chemical or highly corrosive processes.

The impeller 300 in accordance with the present disclosure includesadditional support structures to reinforce the impeller blade assemblies310 against torsional and thermal loads experienced during operation,particularly in high temperature environments. A first support structureis provided in the form of a plurality of blade gussets 330. Each bladegusset 330 is disposed between adjacent impeller blade assemblies 310,and includes a gusset base 332, a long gusset arm 334 and a short gussetarm 336. The gusset base 332 engages and is secured to a correspondingportion of the hub outer surface 304 as best seen in FIG. 14. The longgusset arm 334 extends radially outward from a leading side of thegusset base 332 and engages and is secured to the trailing bladeassembly surface 316 of one of the impeller blade assemblies 310. Theshort gusset arm 336 extends radially outwardly from a trailing side ofthe gusset base 332 and engages and is secured to the leading bladeassembly surface 312 of the adjacent impeller blade assembly 310 in thetrailing direction.

In the illustrated embodiment, the long gusset arms 334 are secured tothe trailing arm surfaces of the blade arms 320. The short gusset arms336 may be secured to the leading surfaces of the blade arms 320, theimpeller blades 322, or both. As shown in FIGS. 12 and 15, each of theimpeller blades 322 has a gusset arm slot 338 extending upward from theinward blade edge by a distance sufficient for the gusset arm slot 338to receive the short gusset arm 336 there in. The gusset arm slot 338allows the short gusset arm 336 to engage the leading arm surface of theblade arm 320, and then the short gusset arm 336 may be welded to theblade arm 320 and/or the impeller blade 322.

As the impeller 300 rotates in the direction 314, the force of the aircreates loads on the impeller blade assemblies 310 in the oppositedirection. The long gusset arms 334 assist in counteracting such loads.Moreover, when installed, the blade gussets 330 may be substantiallyaxially aligned with respect to each other so that the long gusset arm334 of one blade gusset 330 is aligned with the short gusset arm 336 onthe opposite side of the impeller blade assembly 310. This arrangementprovides a unitizing structure whereby the blade arms 320 and the bladegussets 330 define a continuous support disk for the impeller bladeassemblies 310 around the impeller hub 302.

Additional structural support may be provided by a pair of hub sprockets340 disposed on either end of the impeller hub 302 and engaging theimpeller blade assemblies 310. Each of the hub sprockets 340 isgenerally circular with a central sprocket opening 342 (FIG. 15) havingan inner diameter large enough for the hub sprocket 340 to slide overone end of the impeller hub 302. Each hub sprocket 340 further has asprocket outer edge 344 having a plurality of sprocket teeth 346extending radially outward from and circumferentially spaced about thesprocket outer edge 344. The number of sprocket teeth 346 corresponds tothe number of impeller blades 322, i.e., six in the illustratedembodiment. This allows each sprocket tooth 346 to align with andprovide support to one of the impeller blade assemblies 310.

After the blade arms 320 are welded or otherwise secured to the hubouter surface 304, one of the hub sprockets 340 may slide over acorresponding end of the impeller hub 302. The hub sprocket 340 may thenbe rotated until the sprocket teeth 346 aligned with the impeller bladeassemblies 310. Once aligned, the hub sprocket 340 may be pressedagainst the corresponding lateral arm edges of the blade arms 320 andsecured thereto by welds or other appropriate securement means. Thesecond hub sprocket 340 may be installed on the opposite end of theimpeller hub 302 in a similar manner. In some embodiments, the impellerblades 322 may be configured so that the inward blade edge and/orlateral blade edges are also engaged by and secured to the sprocketteeth 346. The sprocket teeth 346 will provide additional support to theimpeller blade assemblies 310 against loads applied opposite thedirection of rotation 314, and against loads tending to twist theimpeller blade assemblies 310. The hub sprockets 340 help to reinforcethe areas of highest stress concentrations and add stability to theblade arms 320. The additional support can prevent cracking between theblade arms 320 and the hub outer surface 304, which tends to be an areawith a high occurrence of failure in high temperature and corrosiveenvironments, and a correspondingly high repair and replacement rate forprevious radial blade impellers.

FIGS. 16-21 illustrate an embodiment of an axial impeller 350 inaccordance with the present disclosure that may be implemented in theindustrial fan assemblies 10, 30. The fan housing 44 would be replacedby an appropriate axial fan housing that would promote axial airflowinto and out of the impeller 350. The impeller 350 includes an impellerhub assembly 352 having a cylindrical shape, a hub assembly outersurface 354 and a hub shaft bore 356 having a hub longitudinal axis 358.In some embodiments, the impeller hub assembly 352 may be a singleunitary component that is forged, cast, machined or otherwise fabricatedfrom a single piece of material. In contrast, in the illustratedembodiment as shown in FIG. 21, the impeller hub assembly 352 may beassembled from multiple components that may be fabricated from a singleor multiple construction materials to form the central structure of theimpeller 350. As shown, the impeller hub assembly 352 includes animpeller hub 360 having a cylindrical shape, a hub outer surface 362,the hub shaft bore 356 with the hub longitudinal axis 358, and a hublongitudinal length. The impeller hub assembly 352 may further include ahub center plate 364 having a center plate inner edge 366, a centerplate outer edge 368, and a hub center plate thickness that is less thanthe hub longitudinal length. The hub center plate 364 is disposed on theimpeller hub 360 with the center plate inner edge 366 engaging andsecured to the hub outer surface 362. As shown in FIG. 20, the hubcenter plate 364 may be located at approximately a longitudinal centerpoint of the impeller hub 360.

Returning to FIG. 21, the impeller hub assembly 352 may further includea hub outer cylinder 370 having an outer cylinder inner surface 372, thehub assembly outer surface 354, and an outer cylinder longitudinallength that is greater than the hub center plate thickness and less thanthe hub longitudinal length. The hub outer cylinder 370 is disposed onthe hub center plate 364 and around the impeller hub 360. The outercylinder inner surface 372 of the hub outer cylinder 370 engages and issecured to the center plate outer edge 368. The hub center plate 364 maybe disposed within the hub outer cylinder 370 at approximately alongitudinal center point of the hub outer cylinder 370 (FIG. 20). Withthis configuration, ends of the impeller hub 360 may extendlongitudinally beyond the corresponding ends of the hub outer cylinder370.

FIG. 16 further illustrates the impeller 350 having a plurality ofimpeller blades 374 circumferentially spaced about the hub assemblyouter surface 354. Each of the impeller blades 374 has a leading bladesurface 376 (FIG. 17) facing a direction of rotation 378 of the impeller350, and a trailing blade surface 380 opposite the leading blade surface376. Each of the impeller blades 374 further has an inward blade edge382 (FIG. 21) secured to the hub assembly outer surface 354, and theimpeller blades 374 extend outward to outward blade edges 384 that areopposite the inward blade edges 382. A first or downstream lateral bladeedge 386 is disposed on a downstream side of the impeller 350 relativeto an airflow direction 388 created when the impeller 350 rotates in thedirection of rotation 378 (FIGS. 17 and 18). A second or upstreamlateral blade edge 390 is disposed opposite the downstream lateral bladeedge 386 on an upstream side of the impeller 350. The impeller blades374 are curved, and in some implementations are slightly twisted into aformed fixture, to promote airflow in the airflow direction 388 andreduce stall and turbulence as the impeller 350 rotates in the directionof rotation 378.

In previous axial impellers used in high temperature environments,impeller blades similar to those illustrated and described herein cantend to flatten and bend, and thereby reduce the airflow efficiency ofand cause vibrations in the industrial fan assemblies 10, 30, make theairflow non-uniform, raise the static pressures, and increase the noisegenerated by the industrial fan assemblies 10, 30. Moreover, over time,cracks can develop at high stress areas found at the point of attachmentof the impeller blades 374 to the hub assembly outer surface 354.Vibration can lead to blade fatigue and the impeller blades 374 candetach from the hub assembly outer surface 354 and project from theimpeller 350 as welds or other fastening systems and the impeller blades374 themselves fail. In addition, dirt, soot, loose insulation, processheat by-products or other types of air stream debris can accumulatewithin the impeller hub assembly 352 in the area between the hub outersurface 362 and the outer cylinder inner surface 372 and cause imbalancein the impeller 350 that can further contribute to vibrations andfailure of the impeller 350. The impeller 350 in accordance with thepresent disclosure provides additional structural support andreinforcement of the impeller blades 374 that can extend the useful lifeof the impeller 350. The structural support may be provided by a firstor downstream cover plate 392 and a second or upstream cover plate 394.

The first cover plate 392 is disposed on a downstream end of theimpeller hub 360 and engages the hub outer cylinder 370. The first coverplate 392 is generally circular with a central cover plate opening 396having an inner diameter large enough for the first cover plate 392 toslide over the downstream end of the impeller hub 360. The first coverplate 392 further has a first cover plate outer edge 398 having a coverplate outer diameter that is at least greater than an inner diameter ofthe outer cylinder inner surface 372 to prevent debris from entering andcollecting in the downstream end of the impeller hub assembly 352. Theflat outer surface of the first cover plate 392 may be flat andrelatively smooth so that air stream debris in the airflow will notadhere to the first cover plate 392. The first cover plate 392 may alsoadd strength to the hub outer cylinder 370. In previous axial bladeimpellers, extreme stresses associated with thermal and torsionalstresses can increase downward of from the impeller blades to the centerof rotation. Many times, the hub outer cylinder 370 and/or the impellerhub 360 will become deformed or will lose their round shape and deforminto an “egg” or other non-symmetrical shape that will cause vibration.The first cover plate 392 supports the impeller hub assembly 352 topreserve the round, symmetrical shape. As shown in the illustratedembodiment in FIG. 20, the cover plate outer diameter may be greaterthan a hub assembly outer diameter of the impeller hub assembly 352 sothat a portion of the first cover plate 392 extends beyond the hubassembly outer surface 354 and engages the first lateral blade edges 386proximate the inward blade edges 382. The overlapping portions of thefirst cover plate 392 and the first lateral blade edges 386 may bewelded or otherwise secured so that the first cover plate 392 supports aportion of the impeller blades 374.

The first cover plate 392 as illustrated further includes a plurality offirst cover plate arms 400 extending outward from and circumferentiallyspaced about the first cover plate outer edge 398. The number of firstcover plate arms 400 corresponds to the number of impeller blades 374,i.e., six in the illustrated embodiment. This allows each first coverplate arm 400 to align with and provide support to one of the impellerblades 374 when the first cover plate arm 400 is secured to the firstlateral blade edge 386 of the impeller blades 374. In the presentembodiment, the first cover plate arms 400 extend the length of theimpeller blades 374 to the outward blade edges 384, and beyond theoutward blade edges 384, to provide support to the entire length of theimpeller blades 374 without disrupting the airflow and maintaining axialairflow velocity uniform along the radial length of the impeller blades374. In axial impeller blades 374, the velocity is low near the hubassembly outer surface 354 and at a maximum at the outward blade edges384 where flattening of the impeller blades 374 may begin to occur. Theextension of the first cover plate arms 400 and corresponding support atthe outward blade edges 384 can greatly reduce the overall flattening ofthe impeller blades 374.

The first cover plate arms 400 are oriented to follow the direction ofthe first lateral blade edges 386 of the impeller blades 374. As shownin FIG. 17, the first cover plate arms 400 extend from the first coverplate outer edge toward the direction of rotation of the impeller 350.The extension of the first cover plate arms 400 may be expressed as afirst plate arm angle θ₁ relative to a radial line 402 from the hublongitudinal axis 358. The first plate arm angle θ₁ may have a valuewithin a range from 20° to 30°. In the illustrated embodiment, the firstplate arm angle θ₁ is approximately equal to 23°.

The second cover plate 394 is disposed on an upstream end of theimpeller hub 360 and engages the hub outer cylinder 370. The secondcover plate 394 has a configuration that is generally similar to theconfiguration of the first cover plate 392, including a central coverplate opening 404 that slides over the upstream end of the impeller hub360, and a cover plate outer edge 406 having the cover plate outerdiameter to cover the upstream end of the impeller hub assembly 352, toextend beyond the hub assembly outer surface 354 and to engage thesecond lateral blade edges 390 proximate the inward blade edges 382. Asmooth relatively flat outer surface that prevents buildup of air streamdebris on the impeller hub 360, and the engagement of the second coverplate 394 with the hub outer cylinder 370 reinforces the impeller hubassembly 352 to preserve its round, symmetrical shape and preventunwanted vibration. Six second cover plate arms 408 extend outward fromand are circumferentially spaced about the second cover plate outer edge406, and extend the length of the impeller blades 374 to the outwardblade edges 384.

The second cover plate arms 408 are oriented to follow the direction ofthe second lateral blade edges 390 of the impeller blades 374. As shownin FIG. 18, the second cover plate arms 408 extend from the second coverplate outer edge away from the direction of rotation 378 of the impeller350. The extension of the second cover plate arms 408 may be expressedas a second plate arm angle θ₂ relative to a radial line 410 from thehub longitudinal axis 358. Due to the curvature of the impeller blades374, the second plate arm angle θ₂ may be greater than the first platearm angle θ₁. Consequently, the second plate arm angle θ₂ may have avalue within a range from 25° to 40°. In the illustrated embodiment, thesecond plate arm angle θ₂ is approximately equal to 31°.

As can be seen in FIG. 19, the curvature of the impeller blades 374 maycause the longitudinal depth of the impeller blades 374 to decrease asthe impeller blades 374 extend away from the hub assembly outer surface354. In the illustrated embodiment, the first lateral blade edges 386have an approximately constant longitudinal position between the inwardblade edge 382 and the outward blade edge 384. The second lateral bladeedges 390 move longitudinally toward the first lateral blade edges 386as the impeller blades 374 extend away from the hub assembly outersurface 354. Consequently, the second cover plate arms 408 extend fromthe second cover plate outer edge 406 at a second plate arm taper angleθ_(T) so that a longitudinal distance between the second cover platearms 408 and the first cover plate arms 400 decreases as the secondcover plate arms 408 extend from the second cover plate outer edge 406.The second plate arm taper angle θ_(T) may have a value within a rangefrom 5° to 10°.

In many implementations, the impellers 20, 260, 300, 350 are disposedwithin the high temperature or corrosive environments, while the fanmount assembly 12, the motor 14 and the transmission 18 are disposed inan ambient environment outside the high temperature environment,separated by an insulating structure such as the insulation dam assembly22. However, because the fan shaft 16 must traverse the boundary betweenthe high temperature and Ambien environments and be able to rotate todrive the impellers 20, 260, 300, 350, heat transfer can occur at theinterface where it may be preferable to thermally isolate theenvironments. Moreover, the high temperature environment in someimplementations may have potentially hazardous gases or particulatematter that should not be permitted to be released into the ambientatmosphere. In some implementations, a controlled atmosphere may beutilized in the process performed within the controlled system, andambient infiltration may yield non-desired results in the process orembrittlement to the finished products. In some processes, a chemical orgas such as nitrogen may be used in the process, such as a heat treatingprocess, and may be injected or otherwise introduced into the hightemperature environment to create a positive pressure in the system.Leakage of the chemical or gas from the enclosed system to the ambientsurroundings through the fan shaft interface can yield undesired resultswithin the process and create a potential hazard to the area surroundingthe controlled system. Therefore, minimizing heat and materialtransmission across the interface may be a requirement in certainimplementations of the industrial fan assemblies 10, 30.

FIGS. 22-25 illustrate an exemplary rotary seal 420 that may beinstalled at a shaft opening through the insulation dam assembly 22 ofthe industrial fan assembly 10 to isolate the high temperatureenvironment and its associated heating and/or chemical process from theambient environment. Referring to FIG. 22, the rotary seal 420 mayinclude a seal housing 422, and a seal cover 424 that may close therotary seal 420 after the fan shaft 16 is inserted through the shaftopening. The seal housing 422 as illustrated may be generallycylindrical, and has a seal housing outer surface 426, a seal housinginner surface 428 (FIG. 23) defining a seal housing bore having a rotaryseal longitudinal axis 430. The seal housing 422 further includes a sealhousing mounting end 432 secured to the stationary structure about ashaft opening through the stationary structure. A seal housing sealingend 434 is disposed opposite the seal housing mounting end 432.

The seal housing inner surface 428 shapes the seal housing bore toreceive the ceiling structures of the rotary seal 420. The seal housinginner surface 428 may extend longitudinally from the seal housingsealing end 434 with an approximately constant seal housing bore innerdiameter. As the seal housing inner surface 428 approaches the sealhousing mounting end 432, the seal housing inner surface 428 extendsradially inward to form a seal housing bore shoulder 436. As the sealhousing inner surface 428 continues to extend toward the seal housingmounting end 432, the seal housing bore may have a seal housing boretapered portion 438 with the seal housing bore inner diameter decreasingas the seal housing inner surface 428 extends axially from the sealhousing bore shoulder 436 toward the seal housing mounting end 432.

The seal housing 422 may have a plurality of seal rings 440, 442, 444disposed within the seal housing bore. The first seal ring 440 may bedisposed proximate the seal housing sealing end 434. The second sealring 442 may be disposed proximate the seal housing mounting end 432 andengaged by the seal housing bore shoulder 436. The seal housing boreouter diameter of the seal housing bore at the seal housing boreshoulder 436 is less than a seal ring outer diameter of the seal rings440, 442, 444 so that the seal housing bore shoulder 436 prevents thesecond seal ring 442 from passing out of the seal housing bore throughthe seal housing mounting end 432. The third seal ring 444 may bedisposed between the first seal ring 440 and the second seal ring 442.

The seal rings 440, 442, 444 may be fabricated from a resilient materialthat is compressible by the seal cover 424. For example, the seal rings440, 442, 444 may be fabricated from graphite rope formed into annuliwith the seal ring outer diameter allowing the seal rings 440, 442, 444to be inserted within the seal housing bore, and a seal ring innerdiameter that allows the fan shaft 16 to be inserted there through.Material such as graphite rope allow the seal rings 440, 442, 444 toform seals with the seal housing inner surface 428 and the shaft outersurface of the fan shaft 16 as discussed further below, while having alow coefficient of friction to allow the fan shaft 16 to rotate withminimal reduction in efficiency of the industrial fan assembly 10.

The seal housing 422 further includes a cavity ring 446 disposed withinthe seal housing bore between the first seal ring 440 and the third sealring 444. The cavity ring 446 has a cavity ring outer diameter that isless than the seal housing bore inner diameter, and a cavity ring innerdiameter that is greater than the shaft outer diameter of the fan shaft16. The cavity ring 446 has a plurality of cavity ring inlet passages448 extending through the cavity ring 446 from a cavity ring outersurface 450 to a cavity ring inner surface 452. The seal housing 422 hasa pressurized inlet passage 454 extending through the seal housing 422from the seal housing outer surface 426 to the seal housing innersurface 428. The cavity ring 446 is aligned with the pressurized inletpassage 454 so that the pressurized inlet passage 454 and the cavityring inlet passages 448 may place the cavity ring inner surface 452 anda corresponding portion of the fan shaft 16 in fluid communication witha pressurized air or fluid source (not shown) fluidly connected to thepressurized inlet passage 454. A pressurized inlet connector 456 may bemounted on the seal housing outer surface 426 around the pressurizedinlet passage 454 to provide a point of connection for a conduitconnecting the pressurized air or fluid source with the rotary seal 420.

The seal cover 424 may be formed from several components to facilitateforming seals within the seal housing bore, and providing additionalsealing around the fan shaft 16 external to the seal housing bore. Theseal cover 424 includes a seal cover flange 460 formed by a seal coverinner ring 462 having an annular shape, and a seal cover outer ring 464having a generally annular shape mounted on an inner ring outer surface466. The seal cover 424 may further include a lip seal 468 mountedwithin an inner ring inner surface 470 of the seal cover inner ring 462.The lip seal 468 may have a compound structure including a lip sealouter bracket 472 secured to the inner ring inner surface 470, a lipseal inner bracket 474 disposed within the lip seal outer bracket 472and providing additional structural support, and a lip seal sealing ring476 mounted to the lip seal outer bracket 472, the lip seal innerbracket 474, or both. The lip seal sealing ring 476 may be formed from aresilient material and have an annular shaft engaging edge 478 that willengage the shaft outer surface to form a lip seal ring seal therebetween when the fan shaft 16 is inserted through the seal cover 424. Alip seal tension band 480 may be disposed on the lip seal sealing ring476 opposite the shaft engaging edge 478 and formed from a stiffermaterial than the lip seal sealing ring 476 to create extra sealingforce against the shaft outer surface in the lip seal ring seal.

The seal cover 424 further includes a seal cover compression ring 482having a hollow cylindrical shape and extending downward from the sealcover flange 460. The seal cover compression ring 482 has a compressionring outer diameter that is less than the seal housing bore outerdiameter proximate the seal housing sealing end 434 so that the sealcover compression ring 482 can be inserted into the seal housing boreand engage the first seal ring 440. The seal cover compression ring 482has a seal ring engagement end 484 opposite the seal cover flange 460.At a compression ring inner surface tapered portion 486 at the seal ringengagement end 484, a compression ring inner diameter may decrease asthe compression ring inner surface tapered portion 486 extends axiallyaway from the seal ring engagement end 484.

The rotary seal 420 also includes a seal cover anchor mechanism engagingthe seal cover 424 and the seal housing 422 to secure the seal cover 424to the seal housing 422. The seal cover anchor mechanism causes the sealcover compression ring 482 to compress the seal rings 440, 442, 444 andcause the seal rings 440, 442, 444 to engage the seal housing innersurface 428 to create a seal ring outer seal there between, and toengage the shaft outer surface of the fan shaft 16 to create a seal ringinner seal there between while allowing the fan shaft 16 to rotaterelative to the seal rings 440, 442, 444. In the illustrated embodiment,the seal cover anchor mechanism includes a plurality of anchor blocks490 mounted on and circumferentially spaced around the seal housingouter surface proximate the seal housing sealing end 434. The seal coveranchor mechanism further includes a plurality of anchor bolts 492extending through anchor bolt apertures 494 that are circumferentiallyspaced around the seal cover flange 460. Each of the anchor bolts 492corresponds to one of the anchor blocks 490 and is received within ananchor block aperture 496 of the corresponding anchor block 490 andtighten therein to compress the seal rings 440, 442, 444 as describedbelow. Because the rotary seal 420 is used for extended periods of time,the seal rings 440, 442, 444 can wear from friction over time. Thecompression on the seal rings 440, 442, 444 can be increased asnecessary over time by tightening the anchor bolts 492 in the anchorblocks 490. This may increase the service life and minimize themaintenance required on the rotary seal 420 by extending the usefullives of the seal rings 440, 442, 444. Moreover, the ability to adjustthe compression on the seal rings 440, 442, 444 can increase theeffectiveness of the rotary seal 420 in preventing unwanted gas andmaterial flow across the interface and reduce maintenance requirementsand undesirable process shut downs.

FIGS. 24 and 25 illustrate the installation of the fan shaft 16 and theclosing and sealing of the rotary seal 420. Referring to FIG. 24, thefirst shaft end 114 of the fan shaft 16 is inserted through the sealcover 424, the seal housing 422 and the shaft opening of the stationarystructure (not shown) such as the insulation dam assembly mounting plate170. The first shaft end 114 may be chamfered for positive engagementand centering of the fan shaft 16 without damaging or rolling the lipseal 468 or the seal rings 440, 442, 444 during insertion. The sealhousing 422 at the seal housing mounting end 432 is welded to theinsulation dam assembly mounting plate 170 to for an air tight sealthere between. A pilot bushing may be used to align the seal housing 422with the mounting plate 170 to ensure axial alignment of the fan shaft16. When the fan shaft 16 is inserted, the shaft engaging edge 478 ofthe lip seal 468 engages the shaft outer surface to form the lip sealring seal, and the seal rings 440, 442, 444 may engage the shaft outersurface to initially form the seal ring inner seals in implementationswhere the seal ring inner diameter is less than the shaft outerdiameter. In such arrangements, the seal housing 422, the seal cover 424and the fan shaft 16 may be substantially axially aligned along therotary seal longitudinal axis 430. As discussed above, the cavity ringouter diameter is less than the seal housing bore inner diameter and thecavity ring inner diameter is greater than the shaft outer diameter soair gaps are present between the seal housing inner surface 428 and thecavity ring outer surface 450, and between the cavity ring inner surface452 and the shaft outer surface.

The rotary seal 420 is closed by screwing the anchor bolts 492 into theanchor bolt apertures 496 of the anchor blocks 490. As the anchor bolts492 are tightened the seal cover 424 is forced toward the seal housing422, the seal rings 440, 442, 444 are compressed between the seal ringengagement end 484 of the seal cover compression ring 482 and the sealhousing bore shoulder 436. As the seal rings 440, 442, 444 arecompressed in the axial direction, they increase in thickness in theradial direction. The seal rings 440, 442, 444 are pressed into the sealhousing inner surface 428 and the shaft outer surface to strengthen theseal ring outer seals and the seal ring inner seals, respectively. Theseal housing bore tapered portion 438 causes compression of the secondseal ring 442 in the radial direction to further increase the seal ringseals proximate the seal housing mounting end 432. The engagement of thefirst seal ring 440 by the compression ring inner surface taperedportion 486 similarly strengthens the seal ring seals proximate the sealhousing sealing end 434.

Even with the sealing ring seals created as described, the rotary seal420 may not be completely airtight. Consequently, a risk may still existfor hazardous gases from the high temperature environment to passthrough the rotary seal 420 and into the ambient environment. The rotaryseal 420 can further prevent the leaking of hazardous gases bypressurizing the seal housing bore. Pressurization may be provided viathe cavity ring 446 and the pressurized inlet passage 454. Pressurizedair or fluid may be supplied by the pressurized air or fluid source (notshown) connected to the pressurized inlet passage 454 by the pressurizedinlet connector 456. The seal rings 440, 442, 444 and the cavity ring446 are dimensioned so that the cavity ring 446 moves axially butremains radially aligned with the pressurized inlet passage 454 afterthe seal rings 440, 442, 444 are compressed by the seal covercompression ring 482. The pressurized air or fluid fills the spacebetween the cavity ring 446 and the seal housing bore, and flows throughthe cavity ring inlet passages 448 to fill the space between the cavityring 446 and the shaft outer surface. In this way, the pressurized airor fluid suppresses flow of gases through both the seal ring inner sealsand the seal ring outer seals. High temperature environment typicallyare not high pressure environments, some modest increases in the airpressure within the seal housing bore may be sufficient to preventleakage of the hazardous gases. However, the air pressure in the sealhousing bore may be increased as necessary to suppress air leakage fromthe high temperature environment in a particular implementation.

INDUSTRIAL APPLICABILITY

The various designs in accordance with the present disclosure canimprove the manufacturability and the performance of industrial fanassemblies. For example, the modular design of the fan mount assembly 12of FIGS. 1 and 3 may allow the industrial fan assembly 10 to beassembled more quickly and simply than previously known mountassemblies. As discussed, the top plate slots 74, 76 and the side platetabs 86, 96 may be dimensioned to provide a relatively tight fit so thatside plates 62, 64 may be approximately properly aligned with respect tothe top plate 60 before being welded to each other and before addingadditional support structures such as the tab gussets 100 and structuralsupport brackets 102, 104. This arrangement may also reduce the totalnumber of components that must be assembled to form the fan mountassembly 12. Further, the motor mount provided by the side plate tabs86, 96 and the motor mounting bracket 130 allow for rapid and simpleadjustment of the position of the motor 14 to achieve the necessarytension within the transmission 18. As the belts or other powertransmission components wear and stretch over time during operation, orcontinuous line starting or the assembly 10 starting and re-starting,the motor mounting bracket 130 allows for fast re-tensioning orreplacement of the components by loosening the motor height adjustmentbolts 158. No other components or power transmission accessories need tobe removed or loosened to gain proper access to defective or worn partsor to re-tension the power transmission accessories. Moreover, onceassembled, the various lift openings 174-180 provide multiple optionsfor attachment to the fan mount assembly 12 for transporting andinstalling the industrial fan assembly 10 in its operating environment.

The reinforcement bars 230 in the impellers 20, 260 provide increasedstructural support to withstand the normal loads and stresses to whichthe impellers 20, 260 will be subject, as well as additional thermalstresses that are experienced in high temperature environments and/orcorrosive chemical environments. The reinforcement bars 230 can unitizethe structure of the impellers 20, 260 so that the loads (torsional,thermal, etc.) experienced by the impeller blades 214, 220, 226, 264during rotation may be transmitted through the impeller rings 216, 222,228, 270 to the reinforcement bars 230 and ultimately to the impellerhub assembly 200. Reduction of the loads and stresses on the less robustcomponents of the impellers 20, 260 can reduce deformation, fatigue,vibration and failure of the components and thereby increase the usefullives of the impellers 20, 260. Additionally, the configuration of theimpeller hub assembly 200 with the impeller hub cone may promote fluidflow through the impellers 20, 260 by facilitating the redirection ofthe air from the axial flow from the fan housing inlet 46 to the radialflow through the impeller blades 214, 220, 226, 264 to the fan housingoutlet 48. The impeller hub cone may further provide additionalstructural support by adding additional welded surface area when theimpeller hub cone is welded to the hub outer surface 304 at the smalldiameter cone end 250 and to the impeller hub backplate 242 at the largediameter cone end 248.

The radial blade impeller 300 and the axial blade impeller 350 inaccordance with the present disclosure are also provided with additionalstructural support of the impeller blades 322, 374, respectively, toextend the useful life of the impellers 300, 350. The hub sprockets 340and their sprocket teeth 346 provide additional support to the impellerblade assemblies 310 proximate the points of connection between theblade arms 320 and the hub outer surface 304 where stress concentrationscan lead to failure of the radial blade impeller 300. The cover plates392, 394 and the cover plate arms 400, 408, respectively, performsimilar structural support for the impeller blades 374 at areas of highstress concentrations. Additionally, the cover plate arms 400, 408reinforce the entire lengths of the impeller blades 374 of the axialblade impeller 350 to maintain the curvature of the impeller blades 374and the efficiency of the industrial fan assemblies 10, 30. In thedesigns of both impellers 300, 350, additional structural support isprovided to the impeller blades 322, 374 without the sprocket teeth 346and the cover plate arms 400, 408, respectively, significantlyencroaching on the airflow paths between the impeller blades 322, 374and through the impellers 300, 350 and creating undesired changes in theairflow.

The rotary seal 420 illustrated and described herein provides isolationof the ambient environment from high temperature and/or chemicallyinduced corrosive environments despite the need to allow rotation of thefan shaft 16 extending there through. Use of seal rings 440, 442, 444having low coefficients of friction, such as those formed from graphiterope, allow seals to be formed around the fan shaft 16 that can preventheat transfer between the environments and leakage of gases and otherparticulate matter without significantly affecting the performance ofthe industrial fan assembly 10, 30. Graphite rope in particular may beresistant to many corrosive materials that may cause degradation inother materials that could be used to fabricate the seal rings 440, 442,444. The effectiveness of the rotary seal 420 may be increased bypressurizing the seal housing bore to suppress leakage of gases throughthe seal ring seals using a neutral or non-contaminating gas orlubricant. The pressurization can prevent leakage of hazardous gasesfrom the high temperature or corrosive environment to the ambientenvironment, and leakage of contaminants from the ambient environmentinto the high temperature environment where specific conditions arerequired for the high temperature operation.

While the preceding text sets forth a detailed description of numerousdifferent embodiments, it should be understood that the legal scope ofprotection is defined by the words of the claims set forth at the end ofthis patent. The detailed description is to be construed as exemplaryonly and does not describe every possible embodiment since describingevery possible embodiment would be impractical, if not impossible.Numerous alternative embodiments could be implemented, using eithercurrent technology or technology developed after the filing date of thispatent, which would still fall within the scope of the claims definingthe scope of protection.

It should also be understood that, unless a term was expressly definedherein, there is no intent to limit the meaning of that term, eitherexpressly or by implication, beyond its plain or ordinary meaning, andsuch term should not be interpreted to be limited in scope based on anystatement made in any section of this patent (other than the language ofthe claims). To the extent that any term recited in the claims at theend of this patent is referred to herein in a manner consistent with asingle meaning, that is done for sake of clarity only so as to notconfuse the reader, and it is not intended that such claim term belimited, by implication or otherwise, to that single meaning.

What is claimed is:
 1. A rotary seal for a rotating shaft passingthrough a stationary structure, the rotary seal comprising: a sealhousing having a seal housing outer surface, a seal housing innersurface defining a seal housing bore having a seal housing longitudinalaxis, a seal housing mounting end secured to the stationary structureabout a shaft opening through which the rotating shaft is inserted, anda seal housing sealing end opposite the seal housing mounting end; aseal ring fabricated from a resilient material and disposed within theseal housing bore and directly engaged by the seal housing inner surfaceto prevent the seal ring from passing out of the seal housing borethrough the seal housing mounting end; a seal cover having a seal coverflange and a seal cover compression ring extending downward from theseal cover flange and having a compression ring outer diameter that isless than a seal housing bore inner diameter proximate the seal housingsealing end so that the seal cover compression ring is inserted into theseal housing bore and directly engages the seal ring to prevent the sealring from passing out of the seal housing bore through the seal housingsealing end; and a seal cover anchor mechanism engaging the seal coverand the seal housing to secure the seal cover to the seal housing,wherein the seal cover anchor mechanism causes the seal covercompression ring to compress the seal ring and cause the seal ring toengage the seal housing inner surface to create a seal ring outer sealthere between and to engage the rotating shaft to create a seal ringinner seal there between while allowing the rotating shaft to rotaterelative to the seal ring.
 2. The rotary seal of claim 1, wherein theseal ring comprises a first seal ring directly engaged by the seal covercompression ring to prevent the first seal ring from passing out of theseal housing bore through the seal housing sealing end and a second sealring directly engaged by the seal housing bore to prevent the secondseal ring from passing out of the seal housing bore through the sealhousing mounting end.
 3. The rotary seal of claim 2, comprising a cavityring disposed within the seal housing bore between the first seal ringand the second seal ring, wherein the cavity ring has a cavity ringouter diameter that is less than the seal housing bore inner diameterand a cavity ring inner diameter that is greater than a shaft outerdiameter, and wherein the first seal ring directly engages the cavityring.
 4. The rotary seal of claim 3, wherein the cavity ring has aplurality of cavity ring inlet passages extending through the cavityring from a cavity ring outer surface to a cavity ring inner surface,wherein the seal housing comprises a pressurized inlet passage extendingthrough the seal housing from the seal housing outer surface to the sealhousing inner surface, and wherein the cavity ring is aligned with thepressurized inlet passage so that the pressurized inlet passage and thecavity ring inlet passages place the cavity ring inner surface and acorresponding portion of the rotating shaft in fluid communication witha pressurized fluid source fluidly connected to the pressurized inletpassage, and wherein the rotary seal comprises a pressurized fluidsupplied by the pressurized fluid source and filling spaces between thecavity ring and the seal housing bore and between the cavity ring and ashaft outer surface and suppressing flow of gases through seal ringinner seals between the shaft outer surface and the first and secondseal rings and through seal ring outer seals between the seal housinginner surface and the first and second seal rings.
 5. The rotary seal ofclaim 4, comprising a pressurized inlet connector mounted on the sealhousing outer surface around the pressurized inlet passage.
 6. Therotary seal of claim 3, wherein the seal ring comprises a third sealring, wherein the first seal ring is disposed between the cavity ringand the seal housing sealing end, and the third seal ring is disposedbetween and directly engaged by the second seal ring and the cavityring.
 7. The rotary seal of claim 3, wherein the seal housing innersurface extends radially inward proximate the seal housing mounting endto form a seal housing bore shoulder that directly engages the secondseal ring to prevent the second seal ring from passing out of the sealhousing bore through the seal housing mounting end.
 8. The rotary sealof claim 7, wherein the seal housing bore inner diameter at the sealhousing bore shoulder is greater than a seal ring inner diameter,wherein the seal housing inner surface has a seal housing bore taperedportion where the seal housing bore inner diameter decreases as the sealhousing inner surface extends axially from the seal housing boreshoulder toward the seal housing mounting end, and wherein the sealhousing bore tapered portion directly engages the second seal ring whenthe seal cover compression ring compresses the first seal ring and thesecond seal ring to cause compression of the second seal ring in aradial direction to increase a seal ring seal between the second sealring and the rotation shaft the proximate the seal housing mounting end.9. The rotary seal of claim 1, wherein the seal cover compression ringhas a seal ring engagement end having a compression ring inner surfacetapered portion where a compression ring inner surface inner diameterdecreases as the compression ring inner surface tapered portion extendsaxially away from the seal ring engagement end, and wherein thecompression ring inner surface tapered portion directly engages the sealring when the seal cover compression ring compresses the seal ring tocause compression of the seal ring in a radial direction to increase aseal ring seal between the seal ring and the rotation shaft theproximate the seal housing sealing end.
 10. The rotary seal of claim 1,wherein the seal cover has a lip seal ring engaging a shaft outersurface and creating a lip seal ring seal there between when therotating shaft is inserted through the seal cover.
 11. The rotary sealof claim 1, wherein the seal cover anchor mechanism comprises: aplurality of anchor blocks mounted on and circumferentially spacedaround the seal housing outer surface proximate the seal housing sealingend; and a plurality of anchor bolts extending through andcircumferentially spaced around the seal cover flange, wherein each ofthe plurality of anchor bolts corresponds to one of the anchor blocksand is received by the one of the anchor blocks and tightened therein tocompress the seal ring.
 12. A rotary seal for a rotating shaft passingthrough a stationary structure, the rotary seal comprising: a sealhousing having a seal housing outer surface, a seal housing innersurface defining a seal housing bore having a seal housing longitudinalaxis, a seal housing mounting end secured to the stationary structureabout a shaft opening through which the rotating shaft is inserted, anda seal housing sealing end opposite the seal housing mounting end; afirst seal ring fabricated from a resilient material and disposed withinthe seal housing bore proximate the seal housing sealing end; a secondseal ring fabricated from the resilient material and disposed within theseal housing bore proximate the seal housing mounting end and directlyengaged by the seal housing inner surface to prevent the second sealring from passing out of the seal housing bore through the seal housingmounting end; a cavity ring disposed within the seal housing borebetween the first seal ring and the second seal ring and directlyengaged by the first seal ring, wherein the cavity ring has a cavityring outer diameter that is less than a seal housing bore inner diameterand a cavity ring inner diameter that is greater than a shaft outerdiameter; a seal cover having a seal cover flange and a seal covercompression ring extending downward from the seal cover flange andhaving a compression ring outer diameter that is less than the sealhousing bore inner diameter proximate the seal housing sealing end sothat the seal cover compression ring is inserted into the seal housingbore and directly engages the first seal ring to prevent the first sealring from passing out of the seal housing bore through the seal housingsealing end; and a seal cover anchor mechanism engaging the seal coverand the seal housing to secure the seal cover to the seal housing,wherein the seal cover anchor mechanism causes the seal covercompression ring to compress the first seal ring and the second sealring and cause the first seal ring and the second seal ring to engagethe seal housing inner surface to create seal ring outer seals therebetween and to engage the rotating shaft to create seal ring inner sealsthere between while allowing the rotating shaft to rotate relative tothe first seal ring and the second seal ring.
 13. The rotary seal ofclaim 12, wherein the cavity ring has a plurality of cavity ring inletpassages extending through the cavity ring from a cavity ring outersurface to a cavity ring inner surface, wherein the seal housingcomprises a pressurized inlet passage extending through the seal housingfrom the seal housing outer surface to the seal housing inner surface,and wherein the cavity ring is aligned with the pressurized inletpassage so that the pressurized inlet passage and the cavity ring inletpassages place the cavity ring inner surface and a corresponding portionof the rotating shaft in fluid communication with a pressurized fluidsource fluidly connected to the pressurized inlet passage, and whereinthe rotary seal comprises a pressurized fluid supplied by thepressurized fluid source and filling spaces between the cavity ring andthe seal housing bore and between the cavity ring and a shaft outersurface and suppressing flow of gases through seal ring inner sealsbetween the shaft outer surface and the first and second seal rings andthrough seal ring outer seals between the seal housing inner surface andthe first and second seal rings.
 14. The rotary seal of claim 13,comprising a pressurized inlet connector mounted on the seal housingouter surface around the pressurized inlet passage.
 15. The rotary sealof claim 12, comprising a third seal ring, wherein the third seal ringis disposed between and directly engaged by the second seal ring and thecavity ring.
 16. The rotary seal of claim 12, wherein the first sealring and the second seal ring are fabricated from graphite rope.
 17. Therotary seal of claim 12, wherein the seal housing inner surface extendsradially inward proximate the seal housing mounting end to form a sealhousing bore shoulder that directly engages the second seal ring toprevent the second seal ring from passing out of the seal housing borethrough the seal housing mounting end, and wherein the seal housing boreinner diameter at the seal housing bore shoulder is greater than a sealring inner diameter.
 18. A rotary seal for a rotating shaft passingthrough a stationary structure, the rotary seal comprising: a sealhousing having a seal housing outer surface, a seal housing innersurface defining a seal housing bore having a seal housing longitudinalaxis, a seal housing mounting end secured to the stationary structureabout a shaft opening through which the rotating shaft is inserted, anda seal housing sealing end opposite the seal housing mounting end; acavity ring disposed within the seal housing bore, wherein the cavityring has a cavity ring outer diameter that is less than a seal housingbore inner diameter and a cavity ring inner diameter that is greaterthan a shaft outer diameter, wherein the cavity ring has a plurality ofcavity ring inlet passages extending through the cavity ring from acavity ring outer surface to a cavity ring inner surface, wherein theseal housing comprises a pressurized inlet passage extending through theseal housing from the seal housing outer surface to the seal housinginner surface, and wherein the cavity ring is aligned with thepressurized inlet passage so that the pressurized inlet passage and thecavity ring inlet passages place the cavity ring inner surface and acorresponding portion of the rotating shaft in fluid communication witha pressurized fluid source fluidly connected to the pressurized inletpassage; a first seal ring fabricated from a resilient material anddisposed within the seal housing bore between the cavity ring and theseal housing sealing end, and directly engaging the cavity ring; asecond seal ring fabricated from the resilient material, disposed withinthe seal housing bore proximate between the cavity ring and the sealhousing mounting end and directly engaged by the seal housing innersurface to prevent the second seal ring from passing out of the sealhousing bore through the seal housing mounting end; a third seal ringfabricated from the resilient material and disposed within the sealhousing bore between the cavity ring and the second seal ring anddirectly engaged by the cavity ring and the second seal ring; a sealcover having a seal cover flange and a seal cover compression ringextending downward from the seal cover flange and having a compressionring outer diameter that is less than the seal housing bore innerdiameter proximate the seal housing sealing end so that the seal covercompression ring is inserted into the seal housing bore and directlyengages the first seal ring to prevent the first seal ring from passingout of the seal housing bore through the seal housing sealing end; aseal cover anchor mechanism engaging the seal cover and the seal housingto secure the seal cover to the seal housing, wherein the seal coveranchor mechanism causes the seal cover compression ring to compress thefirst seal ring, the second seal ring, and the third seal ring, andcause the first seal ring, the second seal ring and the third seal ringto engage the seal housing inner surface to create seal ring outer sealsthere between and to engage the rotating shaft to create seal ring innerseals there between while allowing the rotating shaft to rotate relativeto the first seal ring, the second seal ring and the third seal ring;and a pressurized fluid supplied by the pressurized fluid source andfilling spaces between the cavity ring and the seal housing bore andbetween the cavity ring and a shaft outer surface and suppressing flowof gases through seal ring inner seals between the shaft outer surfaceand the first, second and third seal rings and through seal ring outerseals between the seal housing inner surface and the first, second andthird seal rings.
 19. The rotary seal of claim 18, wherein the firstseal ring, the second seal ring and the third seal ring are fabricatedfrom graphite rope.
 20. The rotary seal of claim 18, wherein the sealhousing inner surface extends radially inward proximate the seal housingmounting end to form a seal housing bore shoulder that directly engagesthe second seal ring to prevent the second seal ring from passing out ofthe seal housing bore through the seal housing mounting end, and whereinthe seal housing bore inner diameter at the seal housing bore shoulderis greater than a seal ring inner diameter.